1. Field of the Invention
The present invention relates to a brushless DC motor, particularly a brushless DC motor used for a fuel pump.
2. Description of the Related Art
In general, a brushless DC motor, called a BLDC motor, is a type of motor where the mechanical contactors, such as a brush and a commutator, are replaced by a switching circuit using a semiconductor, such as a transistor, in order to improve the vulnerability, such as dust created by abrasion of the brush and limited life of the brush.
These BLDC motors are widely used in fields, such as motors for compressors of refrigerators or air-conditioners, and also used for wireless information devices requiring a simple structure, long life, small noise, and high reliability, such as a mobile phone, because they can easily control the speed and have high efficiency throughout the variable speed range.
However, it is another matter to apply the BLDC motors having the above advantages to a fuel pump for vehicles.
In order to apply the BLDC motor to a fuel pump requiring to be highly insulated, particularly it is necessary to ensure performance of an insulating portion that functions as an electric insulator between the stator of the BLDC motor and an outlet connector that functions as a cover housing of the stator.
The structural characteristic and corresponding works require using specific devices for fastening, and bonding, which causes additional processes and deteriorates productivity.
Even with acceptance of the above work, since it is difficult to apply an appropriate standardized reference to assembly of the insulating portion, the insulating portion may be broken by excessive force in screwing a bolt and the quality may be decreased, such as that the bonding portion is detached by an inappropriate amount of application for bonding work or narrowness between the rotator and the stator.
The high product defect ratio causes management for assembly, in accordance with the worker's skill and the environmental conditions, which makes it difficult to increase productivity and achieve an automated process, and as a result, it is difficult to apply BLDC motor to a fuel pump.